The objectives of this project are to determine the chronic toxicity, including carcinogenic potential of twelve chemicals in male and female Fischer 344 rats and B6C3F1 mice. Separate studies are being conducted for five anti-bacterial agents (tetracycline, oxytetracycline, erythromycin, nitrofurazone, and nalidixic acid); three cardiovascular agents (phenylephrine, ephedrine, and methyldopa); two cosmetic dyes (2-amino-4-nitrophenol and 2-amino-5-nitrophenol); and two miscellaneous chemicals (hexylresorcinol and mercaptobenzothiazole). The animals used in these studies were exposed to the chemicals mixed in feed or administered by gavage in corn oil. Results from these studies in experimental animals will be used to establish the relative safety or hazard of these chemicals to humans.